Cryptology ePrint Archive: Report 2011/080

Turbo Codes Can Be Asymptotically Information-Theoretically Secure

Xiao Ma

Abstract: This paper shows that a turbo-coded communication
system can be made secure with a little bit of complexity cost.
The classical permutation ciphers are revisited and analyzed.
Firstly, the ideal stream permutation ciphers are shown to be
asymptotically information-theoretically secure in the sense that
the channel from plaintext to ciphertext has a vanished capacity,
while the practical stream permutation ciphers are shown to
be more secure than the classical stream ciphers in terms of
protecting keys. Secondly, a necessary condition to break down
a block permutation cipher is derived, which is then utilized
to guarantee the computational security of a modified block
permutation cipher. Thirdly, turbo ciphers (turbo-like codes with
private interleavers) are proposed and analyzed.